Java Collections synchronizedMap() Method

The synchronizedMap() method of Java Collections class is used to get a synchronized (thread-safe) map backed by the specified map.

Syntax

Following is the declaration of synchronizedMap() method:

Parameter

Parameter	Description	Required/Optional
m	It is the map which will be wrapped in a synchronized map.	Required

Returns

The synchronizedMap() method returns a synchronized view of the specified Map.

Exceptions

Example 1

import java.util.*;
public class CollectionsSynchronizedMapExample1 {
	public static void main(String[] args) {
		Map<String, String> map = new HashMap<String, String>();
		map.put("1", "Rahul");
		map.put("4", "Karan");
		map.put("3", "Mohan");
		Map<String, String> synmap = Collections.synchronizedMap(map);
		System.out.println("Synchronized map is :" + synmap);	            
	      }
}

Test it Now

Output:

Synchronized map is :{1=Rahul, 3=Mohan, 4=Karan}

Example 2

import java.util.*;
public class CollectionsSynchronizedMapExample2 {
	public static void main(String[] args) {
		Map<Integer, Integer> map = new HashMap<>();
		map.put(1, 1001);
		map.put(2, 1002);
		map.put(3, 1003);
		map.put(4, 1004);
		map.put(5, 1005);
		System.out.println("Map before Synchronized map: " + map);		
		Map<Integer, Integer> synmap = Collections.synchronizedMap(map);	
	      map.remove(4, 1004);
	     System.out.println("Synchronized map after remove(4, 1004):" + synmap);
	     }
}

Test it Now

Output:

Map before Synchronized map: {1=1001, 2=1002, 3=1003, 4=1004, 5=1005}
Synchronized map after remove(4, 1004):{1=1001, 2=1002, 3=1003, 5=1005}

Example 3

import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
public class CollectionsSynchronizedMapExample3 {
	private static AtomicInteger counter = new AtomicInteger();
	public static void main(String[] args) throws  InterruptedException{
	     Map<Integer, Integer> m = new HashMap<>();
	     Map<Integer, Integer> map = Collections.synchronizedMap(m);
	     final ExecutorService e = Executors.newFixedThreadPool(10);
	     for (int i = 0; i < 10000; i++) {
	            e.execute(() -> map.put(counter.incrementAndGet(),
	            (int) (Math.random() * 100)));
	            }
	     e.shutdown();
	     e.awaitTermination(1000, TimeUnit.SECONDS);
	     System.out.println(map.size());//should be 10000		
	     }
}

Test it Now

Output:

Next TopicJava Collections Class

← prev next →